This application claims the priority of Japanese Patent application No.2001-182640 filed on Jun. 15, 2001, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ultraviolet absorbent, a photostabilizer, and an ultraviolet ray-absorbing composition, a photostabilized composition and an external preparation for skin, which includes with an ultraviolet absorbent or a photostabilizer. Particularly, the invention relates to the improvement of the stability thereof and the use thereof.
2. Background Art
Among ultraviolet sunlight, ultraviolet ray of a wavelength below 290 nm is absorbed in the ozone layer, so such ultraviolet ray never reaches the ground surface. Ultraviolet ray of 290 nm to 400 nm reaches the ground surface and give various influences. From the standpoint of dermatology, it has been known that ultraviolet ray of a medium wavelength of 290 nm to 320 nm triggers erythema, blistering, melanism activation and chromatosis. Because ultraviolet ray of a long wavelength of 320 nm to 400 nm has an instantaneous melanism action to darken skin immediately after its irradiation and the energy reaches dermis, additionally, it is said that the ultraviolet ray influences the elastic fibers in vascular walls and connective tissues. These actions of medium- to long-wave ultraviolet ray promote skin senility so that these are believed to be one of causes generating spots, freckles, and wrinkles and the like.
For skin protection against such ultraviolet ray, ultraviolet absorbents such as benzotriazole derivatives, benzophenone derivatives, salicylic acid derivatives, p-aminobenzoic acid derivatives, cinnamic acid derivatives and urocanic acid derivatives have been used.
These ultraviolet absorbents are also used as photostabilizers for pigments, perfume, drugs and the like which are used in medical supplies and cosmetics.
Further, ultraviolet absorbents have been used in fields other than the fields of medical supplies and cosmetics. For example, ultraviolet absorbents have been used to give ultraviolet ray prevention effect to various materials such as paints, dyes, pigments, various resins, synthetic rubber, latex, film, fiber and glass, by adding the ultraviolet absorbents to these materials or coating these materials with the ultraviolet absorbents. Hence, the resulting products or the films thereof or products coated with the films can be protected against ultraviolet ray. Thus, the ultraviolet absorbents can prevent ultraviolet deterioration and modification to maintain their qualities.
Preferably, ultraviolet absorbents can absorb the whole ultraviolet wavelength range of 290 nm to 400 nm. Importantly, ultraviolet absorbents should not have any skin irritation when included in external preparations for skin. Furthermore, importantly, ultraviolet absorbents should not be decomposed under daylight exposure.
However, the ultraviolet absorbents of the related art are not necessarily satisfactory from these views. Further, the ultraviolet absorbents of the related art eventually cause coloring or deposition when used in combination with inorganic powder-based ultraviolet shielding agents commonly used in external preparations for skin. Accordingly, a more satisfactory photostabilizer has been demanded.
Ultraviolet absorbents of the related art in fields other than the fields of medical supplies and cosmetics have been disadvantageous in that the ultraviolet absorbents sublime or vaporize under heating during sintering of film or during resin molding and in that the ultraviolet absorbents gradually vaporize over time even without heating, leading to the attenuation of the effect.
In such circumstances with the problems of the related art, the present invention has been attained. It is a purpose of the invention to provide an ultraviolet absorbent and a photostabilizer, both having excellent absorption over a wide range of ultraviolet wavelengths as well as great stabilities together with great safety. It is an additional purpose of the invention to provide an ultraviolet-absorbing composition and a photostabilized composition, in both of which is included the ultraviolet absorbent or the photostabilizer. It is a further purpose of the invention to provide an external preparation for skin, in which the ultraviolet absorbent or the photostabilizer is included.
So as to achieve the purposes, the inventors have made investigations. Consequently, the inventors have found that a certain type of pyridazine derivatives have such properties as described above that the pyridazine derivatives are great ultraviolet absorbents and photostabilizers. Thus, the invention has been achieved.
In other words, the ultraviolet absorbent and the photostabilizer of the invention contain as the effective ingredient the following pyridazine derivative with great absorption over a wide range of ultraviolet wavelengths and with great stability and safety and a salt thereof. 
wherein R1 and R4 independently represent hydrogen atom, hydroxyl group, a lower alkyl group, a lower alkoxyl group or N R5, R6 group, wherein R5 and R6 may be the same or different and represent hydrogen atom, a lower alkyl group, or a lower hydroxyalkyl group; or R5 and R6 taken together with nitrogen atom represent a heterocyclic group selected from the group consisting of aziridinyl group, azetidinyl group, pyrrolidinyl group, piperidino group, hexahydroazepinyl group, heptamethylene imino group, octamethylene imino group, morpholino group, thiomorpholino group, piperazinyl group, and 4-lower alkylpiperazinyl group; R2 and R3 independently represent hydrogen atom, bromine atom, chlorine atom, hydroxyl group, a lower alkyl group, or a lower alkoxyl group or N R7, R8 group, wherein R7 and R8 may be the same or different and represent hydrogen atom, a lower alkyl group, or a lower hydroxyalkyl group; or R7 and R8 taken together with nitrogen atom represent a heterocyclic group selected from the group consisting of aziridinyl group, azetidinyl group, pyrrolidinyl group, piperidino group, hexahydroazepinyl group, heptamethylene imino group, octamethylene imino group, morpholino group, thiomorpholino group, piperazinyl group, and 4-lower alkylpiperazinyl group; wherein R1, R2, R3 and R4 are not simultaneously hydrogen atom and R2 and R3 are not simultaneously morpholino group.
The ultraviolet-absorbing composition of the invention characteristically includes the above-mentioned ultraviolet absorbent.
The photostabilized composition of the invention characteristically includes the above-mentioned ultraviolet absorbent.
The external preparation for skin in accordance with the invention characteristically includes the above-mentioned ultraviolet absorbent. Preferably, the external preparation for skin in accordance with the invention further includes an inorganic powder.
Additionally, the external preparation for skin in accordance with the invention includes the photostabilizer. Preferably, the external preparation for skin in accordance with the invention further includes sequestering agents.
Still additionally, the pyridazine derivative and/or a salt thereof is preferably included at 0.001 to 20 wt % in the external preparation for skin in accordance with the invention.